Polymerization catalyst compounds are typically combined with an activator (or co-catalyst) to yield compositions having a vacant coordination site that will coordinate, insert, and polymerize olefins. Metallocene polymerization catalysts are typically activated with aluminoxanes which are generally oligomeric compounds containing —Al(R)—O— subunits, where R is an alkyl group. The most common alumoxane activator is methylalumoxane (MAO), produced by the hydrolysis of trimethylaluminum (TMA). MAO, however, is expensive to utilize because it must be present in great excess relative to the metallocene and because of the high cost of TMA. In addition, MAO tends to be unstable as it precipitates out of solution over time.
In addition, metallocene polymerization catalyst systems, utilized in industrial slurry or gas phases processes, are typically immobilized on a carrier or support, for example silica or alumina. Metallocenes are supported to enhance the morphology of the forming polymeric particles such that they achieve a shape and density that improves reactor operability and ease of handling. Metallocene catalysts, however, typically exhibit lower activity when supported when compared to the corresponding non-supported catalyst systems.
Alternative activators for metallocenes and other single-site polymerization catalysts have been discovered in recent years. For example, perfluorophenyl aluminum and borane complexes containing one anionic nitrogen containing group may activate metallocenes. For example, R. E. LaPointe, G. R. Roof, K. A. Abboud, J. Klosin, J. Am. Chem. Soc. 2000, 122, 9560-9561, and WO 01/23442 A1 report the synthesis of (C6F5)3A1(imidazole)A1(C6F5)3][HNR′R″]. In addition, G. Kehr, R. Fröhlich, B. Wibbeling, G. Erker, Chem. Eur. J. 2000, 6, No.2, 258-266 report the synthesis of (N-Pyrrolyl)B(C6F5)2.
U.S. Pat. Nos. 6,147,173 and 6,211,105 disclose a polymerization process and polymerization catalyst where the catalyst includes an activator complex having a Group 13 element and at least one halogenated, nitrogen-containing aromatic group ligand.
In light of the high cost and low stability of MAO and of the reduced activity when metallocenes are supported, there is a need in the art for new inexpensive, stable and supportable polymerization catalyst activator compounds. There is also a need in the art for methods for preparing these activator compounds, polymerization catalyst systems including these activator compounds and for polymerization processes utilizing the same.